${9 \div 0.9 = {?}}$
Answer: $ {9 \div 0.9 = 9 \div \dfrac{9}{10}} $ Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. $ {9 \div \dfrac{9}{10} = 9 \times \dfrac{10}{9}} $ $ {\phantom{9 \div \dfrac{9}{10}} = \dfrac{9 \times 10}{9}} $ $ {\phantom{9 \div \dfrac{9}{10}} = \dfrac{90}{9}} $ $ {\phantom{9 \div \dfrac{9}{10}} = 10} $